Connection performance uniformity improving method for assembly joint surface based on partition hardening

A method for improving uniformity of connection performance of assembly surfaces based on zoned hardening, comprising:

• 1) Dividing, based on a size D, which is a spot of a pulsed laser of a laser device to be used, a mating surface to be hardened of the assembly surfaces into N sub-regions, where N=P×Q, and P and Q are integers, wherein the assembly surface adopts surfaces adopt a non-uniform zoned hardening layout;
• 2) obtaining, when a sub-region T of the mating surface to be hardened comprises a number n of finite element meshes, an elastic modulus of a region of a finite element mesh i is ei, an area of the region of the finite element mesh i is si, and a hardening thickness of the region of the finite element mesh i is hi, an equivalent elastic modulus ET and an equivalent hardening thickness HT of the sub-region T of the mating surface to be hardened;
• 3) storing the equivalent elastic moduli ET and the equivalent hardening thicknesses HT of the N sub-regions of the mating surface to be hardened respectively in a matrix of P×Q, that is, [E]P×Q and [H]P×Q;
• determining, then based on that, pulse energies NL, pulse frequencies PL, and pulse widths MK of the pulsed laser, and storing the pulse energies NL, the pulse frequencies PL, and the pulse widths MK of the pulsed laser respectively in a matrix of P×Q, that is, a pulse energy matrix [NL]P×Q, a pulse frequency matrix [PL]P×Q and a pulse width matrix [MK]P×Q of the pulsed laser;
• and
• 4) performing zoned laser hardening, by laser hardening equipment, by using a zoning information matrix [N]P×Q of the mating surface to be hardened, the pulse energy matrix [NL]P×Q, the pulse frequency matrix [PL]P×Q and the pulse width matrix [MK]P×Q of the pulsed laser as control signals or parameters of the laser hardening equipment,
• wherein in step 1), the adopted non-uniform zoned hardening layout of the assembly surfaces is specified that:
• the assembly surfaces comprise a first mating surface and a second mating surface matching the first mating surface, and non-uniform zoned hardening is designed on the first mating surface, the second mating surface, or both the first mating surface and the second mating surface,
• wherein the designing of the non-uniform zoned hardening on the first mating surface, the second mating surface, or both the first mating surface and the second mating surface comprises:
• (A) dividing finite element meshes for the assembly surfaces, setting elastic moduli of the materials, and constructing a finite element model for contact analysis of the assembly surfaces;
• (B) performing finite element contact analysis and outputting contact pressure and connection stiffness of the mating surface, and respectively calculating a contact pressure discrete degree θp and a connection stiffness discrete degree θs;
• (C) respectively calculating a relative change rate Δp of the contact pressure discrete degree and a relative change rate Δs of the connection stiffness discrete degree between two adjacent optimization iteration steps;
• (D) constructing a connection performance uniformity optimization design objective function Δ, based on a weight factor c between the contact pressure discrete degree and the connection stiffness discrete degree, where an optimization design objective is minΔ, where the connection performance uniformity optimization design objective function Δ is calculated as follows,
• Δ=−[c·Δp+(1−c)·Δs],c∈[0,1];
• (E) terminating optimization, and outputting and saving elastic modulus data of the materials, when the connection performance uniformity optimization design objective function Δ satisfies Δ≤ε, or a number k of optimization iteration steps satisfies k≤N;
• otherwise, performing step (F) and step (G);
• (F) defining a region where a zoned hardening optimization design is to be carried out, taking an elastic modulus of a material of the region as an optimization design variable, setting an acceleration constant factor α and a relaxation constant factor β, and in a new optimization iteration step (k+1), optimizing and updating the elastic modulus of the material of the zoned hardening optimization design region;
• and
• (G) updating the finite element model of the assembly surfaces described in step (A) based on a new value of the elastic modulus of the material obtained in step (F), and performing a new finite element contact analysis, and
• wherein in step (F), the elastic modulus of the material of the zoned hardening optimization design region is optimized and updated by using one of following two formulas:
• e
• j
• k
• +
• 1
• =
• e
• j
• k
• -
• α
• ·
• ∂
• c
• ·
• θ
• p
• +
• (
• 1
• -
• c
• )
• ·
• θ
• s
• ∂
• e
• j
• ·
• e
• j
• k
• ,
• e
• j
• k
• +
• 1
• =
• β
• ×
• e
• j
• 0
• ×
• [
• c
• ·
• σ
• max
• k
• σ
• j
• k
• +
• (
• 1
• -
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• )
• ⁢
• δ
• max
• k
• δ
• j
• k
• ]
• ×
• [
• c
• ·
• σ
• min
• k
• σ
• j
• k
• +
• (
• 1
• -
• c
• )
• ⁢
• δ
• min
• k
• δ
• j
• k
• ]
• ,
• where ej denotes an elastic modulus of a finite element mesh j in a design domain, where j=1, 2, 3, . . . , M, and M denotes a total number of finite element meshes in the design domain, σ denotes an element Von Mises stress, and σmax and σmin denote maximum and minimum values of the element Von Mises stress on a contact interface, δ denotes an element connection stiffness, and δmax and δmin denote maximum and minimum values of the element connection stiffness on the contact interface.