Tube expansion process

A process for expanding a plastically deformable conduit surrounded by a structure of substantially less elasticity relative to said conduit in order to reduce the clearance between said conduit and said surrounding structure, comprising the steps of:

• (a) applying a radially expansive pressure to said conduit to plastically expand said conduit;
• (b) sensing when said conduit contacts said surrounding structure, and determining the value of the radially expansive pressure at the time contact is made;
• (c) increasing said value of the radially expansive pressure by a variable amount whose value is solely dependent upon the value of the pressure at contact, and
• (d) removing said radially expansive pressure from said conduit.

A process for expanding a platically deformable conduit along an axial section surrounded by a structure of substantially less elasticity relative to said conduit in order to reduce the clearance between said conduit and said surrounding structure, comprising the step of:

• (a) applying a radially expansive pressure which increases as a function of time to said axial section of said conduit to plastically expand said section of said conduit;
• (b) sensing when said axial section of conduit contacts surrounding structure, and determining the value of the radially expansive pressure at the time such contact is made;
• (c) increasing said contact value of the radially expansive force by a variable percentage, whose specific value is dependent upon the value of the contact pressure, and
• (d) decreasing said radially expansive pressure to zero.

A process for expanding a metallic conduit extending through a bore in a plate in order to reduce the clearance between the conduit and the bore, comprising the steps of:

• (a) applying a radially expansive pressure which increases as a function of time to the inside of the section of conduit circumscribed by the walls of said bore until said conduit contacts the walls of said bore;
• (b) determining the value of the radially expansive pressure when said section of conduit contacts the walls of said bore;
• (c) increasing said radially expansive contact pressure by an amount which is dependent upon the value of the contact pressure, and
• (d) decreasing said radially expansive force to zero.

A process for expanding a metallic tube extending through a bore in a plate in order to reduce an annular clearance between the tube and the bore comprising the steps of:

• (a) applying a radially expansive pressure within the tube along the longitudinal portion of the tube surrounded by the bore wherein said pressure generally increases as a function of time;
• (b) monitoring the slope of the curve defined by pressure over time as the pressure increases and in order to determine (i) whether the tube is expanding at a rate which will induce a substantial amount of work-hardening to occur in the walls thereof during the elastic deformation of the tube, as well as (ii) the value of the pressure at an inflection point indicative of contact between said longitudinal portion of said tube and said bore;
• (c) determining a final expansion pressure by multiplying the value of the pressure at contact by about 106% when said contact pressure is below about 8,000 psi, and by multiplying the value of the pressure at contact by about 110% when said contact pressure is above about 8,000 psi, and
• (d) applying said final expansion pressure to said tube.

A process for expanding and plastically deforming metallic sleeve into engagement with an elastically deformable metallic tube in order to produce an interference joint therebetween, comprising the steps of:

• (a) applying a radially expansive pressure within the sleeve along a longitudinal portion of the tube surrounded by the tube wherein said pressure generally increases as a function of time at a rate which will not cause a substantial amount of work-hardening to occur in the walls thereof during the elastic deformation of the tube and the sleeve;
• (b) monitoring the slope of the curve defined by pressure over time in order to determine the value of the pressure immediately before the occurance of an inflection point in the curve which is indicative of a plastic deformation of both the sleeve and the surrounding tube;
• (c) determining a final expansion pressure by projecting a line which originates at said point located immediately before said inflection point, said whose slope is between about 6 to 8 percent less than the slope of the pressure curve at said point, and
• (d) removing said radially expansive pressure from said sleeve when said pressure curve intersects with said projected line.

A process for expanding a portion of a plastically deformable conduit surrounded by a structure in order to engage the conduit portion against said structure, comprising the steps of:

• (a) applying a radially expansive pressure to said conduit portion which increases as a function of time;
• (b) monitoring both the value and the slope of the function defined by pressure over time in order to determine the time at which an inflection point occurs which is indicative of an engagement between said conduit portion and said surrounding structure;
• (c) noting the value and the slope of the pressure function in the vicinity of said inflection point;
• (d) computing a final expansion pressure by adding an additional amount of pressure onto the noted pressure value, wherein the value of said additional pressure is a variable which is solely dependent on at least said noted pressure value in the vicinity of said inflection point, and
• (e) applying said final expansion pressure to said conduit portion.