Constitutive strength model for spot joints of thin-walled energy-absorbing elements

• Published in: Engineering structures 2023-10, Vol.292, p.116592, Article 116592
• Main Authors: Kaczyński, Paweł, Makuła, Piotr
• Format: Article
• Language: English
• Subjects: Clinching; Crashworthiness; Thin-walled structure; Top-hat; Welding
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2023.116592

[Display omitted] •A method to determine the strength criterion causing failure of spot joints used in the construction of thin-walled profiles under impact load has been developed and strength parameters guaranteeing joint continuity during dynamic crushing of crash–boxes were determined.•Extensive quasi-static and dynamic materials tests were conducted for the 5 most popular steel grades used in the automotive industry (DP600, DP800, DP1000, HSLA and DC01A).•The strength of spot joints in a complex load state was evaluated and numerical simulations were performed to predict the behavior (shearing force, cross–tension force) of the clinched and spot-welded joints.•Both quasi-static and dynamic crushing of thin-walled, energy-absorbing, top-hat structures were conducted and compared with presented constitutive strength models which allowed to calibrate the FEM models.•The constitutive models for the minimum shear strength (Fs) and cross-tension strength (Fn) of joints was determined as a function of sheet thickness and parameters Re and Rm. The goal of this paper was to determine the strength criterion that causes the failure of point-to-point joints of thin-walled profiles under impact load, as well as to determine the strength parameters that guarantee joint continuity during dynamic folding of crash boxes. For this purpose, extensive quasi-static and dynamic materials tests were conducted for the five most popular steel grades used in the automotive industry: DP600, DP800, DP1000, HSLA and DC01. The strength of the spot joints was investigated in acomplex load state using the original instrumentation. This allowed authors to build and validate mathematical models of the load-bearing capacity of point-to-point joints and to conduct simple and efficient numerical simulations of these elements without the need to account for their geometry. Following the validation of mathematical models and load-bearing models of the joints, extensive experiments of quasi-static and dynamic crushing of thin-walled energy-absorbing top-hat (TH) structures were conducted. The data collected made it possible to calibrate the FEM model correctly and conduct numerical simulations of the dynamic crushing of energy-absorbing structures. As a result, the minimum shear strength (Fs) and cross-tension strength (Fn) of the joints were determined as a function of the sheet thickness and the parameters of Re and Rm. The creation of any spot joint enabling the simultaneous carrying of