Optimized fastener construction system and method

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a smooth shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said smooth shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings, said smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided, the axial widths of said pin grooves and shoulders and said collar grooves and shoulders being preselected in accordance with the relative shear strengths of said different materials whereby said collar shoulders are adapted to fail in shear generally at said design tensile load and said pin shoulders at around 110% of said design tensile load applied between said pin member and said collar,
• said collar having a minimum wall thickness, and hence weight, such that after swage compressive yielding could occur generally at around 110% of said design tensile load,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin grooves into which said collar is swaged.

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a smooth shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said smooth shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings, said smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the pin member having a higher ultimate shear stress than said collar with the ultimate shear stress of said collar being selected to be generally as high as possible without crushing said pin member during swage,
• said collar having a minimum wall thickness, and hence weight, such that, after swage, compressive yielding could occur generally at said design tensile load,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin lock grooves into which said collar is swaged.

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight for the material utilized, said fastener comprising:

• a pin member having an elongated shank including a smooth shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said smooth shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings, said smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin lock grooves into which said collar is swaged.

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a smooth shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a groove portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said smooth shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings, said smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided,
• said colar having a minimum wall thickness, and hence weight, such that, after swage, compressive yielding could occur generally at said design tensile load,
• said pin member prior to swage having a pintail portion connected with said grooved portion by a breakneck groove, said pintail portion adapted to be gripped by a tool actuable for applying a relative axial force between said pin member and said collar, said breakneck groove adapted to accept a combined tensile and bending load and to fracture at a preselected axial force after completion of swaging, said breakneck groove having a stress concentration factor providing for fracture at said preselected axial force and further providing for fracture within around 12% from said preselected axial force when said fastener is applied to workpieces having its collar engaging surface at an angle of 7.degree. normal to the axis of said pin member, said stress concentration factor (Kt) being expressed by the relationship:
• (d/D) (Kt) where `d` is the minimum diameter of said breakneck groove and D is the diameter of said pintail portion immediately adjacent said breakneck groove, said relationship being approximately 1.6 for said fastener for application in the aligned openings of around 3/16" diameter where said smooth shank portion is around 0.189".

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight, the fastener comprising a pin member having an elongated shank including a smooth shank portion adapted to be located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, the smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar adapted to be swaged into said pin grooves whereby the workpieces are fastened together, said collar when swaged having collar grooves and shoulders interlocking said pin grooves and shoulders, the method of optimizing the fastener comprising the steps of:

• forming the smooth shank portion to be of a preselected length relative to the combined thickness of the workpieces whereby the grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings,
• forming the tubular collar to have a minimum length sufficient to overlay and to be swaged into the pin grooves,
• forming the pin member and collar from different materials having ultimate shear stresses with different magnitudes with the ratio of such shear stresses of the pin member to the collar being such that the pin member will substantially resist crushing during swage,
• forming the pin grooves and shoulders of preselected axial widths in accordance with the relative shear strengths of the different materials of the pin member and collar whereby the pin shoulders and collar shoulders formed in swaging will fail in shear generally at the design tensile load applied between the pin member and collar, the collar when formed having a predetermined volume of material which is at least around 20% greater than that required to fill the pin grooves when swaged to a minimum wall thickness, and
• swaging the collar to the minimum wall thickness which has a magnitude such that compressive failure could occur generally at the design tensile load.

In a fastening system, including a two piece fastener, for securing a plurality of workpieces together with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener optimized to meet said design shear and tensile loads with a minimum weight, the fastener comprising a pin member having an elongated shank including a smooth shank portion adapted to be located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, the smooth shank portion being of a diameter sufficient to provide the necessary shear strength to accept said design shear load, a tubular collar adapted to be swaged into said pin grooves whereby the workpieces are fastened together, said collar when swaged having collar grooves and shoulders interlocking said pin grooves and shoulders, the method of optimizing the fastener comprising the steps of:

• forming the smooth shank portion to be of a preselected length relative to the combined thickness of the workpieces whereby the grooved portion will be located outside of and extend for a minimum length beyond the confines of the aligned openings,
• forming the tubular collar to have a minimum length sufficient to overlay and to be swaged into the pin grooves, the collar when formed having a predetermined volume of material which is at least around 20% greater than that required to fill the pin grooves when swaged to a minimum wall thickness, and
• swaging the collar to the minimum wall thickness which has a magnitude such that compressive yielding could occur generally at the design tensile load.

In a fastening system, including a fastener, for securing a plurality of workpieces within a selected grip range from a minimum to a maximum thickness and with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said fastener constructed to meet said design shear and tensile loads with a preselected minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will generally extend for a minimum length beyond the confines of the aligned openings for the workpieces having a combined thickness at the maximum thickness of workpieces, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided, the axial widths of said pin grooves and shoulders and said collar grooves and shoulders being preselected in accordance with the relative shear strengths of said different materials whereby said pin shoulders and said collar shoulders are adapted to fail in shear generally at said design tensile load applied between said pin member and said collar,
• said collar having a miniumu wall thickness such that after swage compressive yielding could occur generally at said design tensile load,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin grooves into which said collar is swaged.

In a fastening system, including a fastener, for securing a plurality of workpieces within a selected grip range from a minimum to a maximum thickness and with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said two piece fastener constructed to meet said design shear and tensile loads with a preselected minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will generally extend for a minimum length beyond the confines of the aligned openings for the workpiece having a combined thickness at the maximum thickness of workpieces, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided, the axial widths of said pin grooves and shoulders and said collar grooves and shoulders being preselected in accordance with the relative shear strengths of said different materials whereby said collar shoulders are adapted to fail in shear generally at said design tensile load and said pin shoulders at around 110% of said design tensile load applied between said pin member and said collar,
• said collar having a minimum wall thickness such that after swage compressive yielding could occur generally at around 110% of said design tensile load,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin grooves into which said collar is swaged.

In a fastening system, including a fastener, for securing a plurality of workpieces within a selected grip range from a minimum to a maximum thickness and with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said fastener constructed to meet said design shear and tensile loads with a preselected minimum weight for the materials utilized, said fastener comprising:

• a pin member having an elongated shank including a shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said shank portion of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will generally extend for a minimum length beyond the confines of the aligned openings for the workpieces having a combined thickness at the maximum thickness of workpieces, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the pin member having a higher ultimate shear stress than said collar with the ultimate shear stress of said collar being selected to be generally as high as possible without crushing said pin member during swage,
• said collar having a minimum wall thickness such that, after swage, compressive yielding could occur generally at said design tensile load,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin lock grooves into which said collar is swaged.

In a fastening system, including a fastener, for securing a plurality of workpieces within a selected grip range from a minimum to a maximum thickness and defining a selected grip range with the fastening system having a required preselected magnitude of design shear load and a required preselected magnitude of design tensile load and with said fastener constructed to meet said design shear and tensile loads with a preselected minimum weight for the material utilized, said fastener comprising:

• a pin member having an elongated shank including a shank portion located in aligned openings in the workpieces and terminating in one end in an enlarged head and at its opposite end in a grooved portion comprising a plurality of circumferentially extending pin grooves and associated pin shoulders, said shank portion being of a preselected length relative to the combined thickness of the workpieces such that said grooved portion will generally extend for a minimum length beyond the confines of the aligned openings for the workpieces having a combined thickness at the maximum thickness of workpieces, a tubular collar swaged into said pin grooves whereby the workpieces are fastened together, said tubular collar being of a minimum length sufficient to overlay and to be swaged into said pin grooves, said swaged collar having collar grooves and shoulders interlocking said pin grooves and shoulders, said pin member and said collar being of different materials having ultimate shear stresses of different magnitudes with the ratio of such shear stresses of said pin member to said collar being such that crushing of said pin member in swage is substantially avoided,
• said collar being swaged into said pin grooves via a swage anvil having an effective throat swage portion,
• said collar having a predetermined volume of material which is generally at least around 20% greater than the available volume defined by said effective throat swage portion and the confronting portion of said pin lock grooves into which said collar is swaged.