Preparation, microstructure and mechanical properties of CP-Ti/AA6061-Al laminated composites by differential temperature rolling with induction heating

Residual stress measurement of single point incremental formed Al/Cu bimetal using incremental hole-drilling method

Incremental sheet forming for prototyping automotive modules

Surface roughness affects the performance and service life of the formed components. To this end, efforts have been spent in the innovative incremental sheet forming (ISF) process. However, the researchers yet have not reached any agreement regarding the process effects on roughness. This demands further research to comprehend the knowledge in order to acquire a threshold level of understanding on surface roughening in the process. The present study investigates the processing effects upon the roughness of interior surfaces and on the friction indicator at the tool/sheet interface during forming of an aluminum sheet. Some of the sparsely studied parameters, namely flow stress, sheet thickness, and forming angle, are undertaken besides commonly considered ones (i.e., tool diameter and step size). The analysis of the results reveals that the friction indicator and roughness are analogous in respect of their response to parameter variations. Further, the roughness in general linearly increases with an increase in the friction indicator because the sheet abrasion correspondingly increases as revealed by the SEM-based surface morphology. A combination of parameters, among several attempted ones, namely dsinθ/2pt (where d is the tool diameter, θ is the forming angle, p is the step size, and t is the sheet thickness), is identified to have controlling influence on the roughness of interior surfaces. This combination is validated employing two materials namely Al1060 and Cu/Steel composite. In this combination, the factor d/2p followed by 1/t is found to have the greatest contribution towards the roughening of surfaces. Moreover, the value of this combination is proposed to keep low in order to produce components with good finish, say ≤ 50 mm−1 for Al10160 and 20 mm−1 for Cu/Steel composite. The present and past roughness studies in ISF are also compared, which reveals that the parameters effects are associated to the type of material.

Surface roughness as the function of friction indicator and an important parameters-combination having controlling influence on the roughness: recent results in incremental forming

Disc springs are conical annular discs, which are characterized by a high spring force with a small spring travel and good space utilization. In operation, they must meet high demands on the stability of the spring characteristic and the fatigue strength. Under loading, tensile stresses occur which limit the possible applications of disc springs. Compressive stresses can be generated in the stressed areas by means of shot-peening in order to extend the operating limits for a given yield and fatigue strength. Since the spring geometry and characteristics change during shot-peening, the design of the shot-peening treatment is iterative and cumbersome. The present research proposes an incremental forming process for forming and integrated targeted adjustment of residual stresses in disc springs from metastable austenitic stainless steel (MASS), to achieve improved spring properties and high cyclic strength. The main mechanism of residual stress generation is the transformation of metastable austenite into martensite under the action of the forming tool. Different experimental characterization techniques like the hole drilling method, X-ray diffraction, disc compression tests, optical microscopy and cyclic tests are used to correlate the residual stresses and disc spring properties. A numerical model is developed for simulating the martensite transformation in disc springs manufacturing. The results prove that incremental forming enables process-integrated engineering of the desired compressive residual stresses, entailing a higher spring force of metastable austenitic disc springs in comparison to conventional disc springs. Due to martensite formation, the generated residual stresses are stable under cyclic loading, which is not the case for conventionally manufactured springs.

Integrated Forming and Surface Engineering of Disc Springs by Inducing Residual Stresses by Incremental Sheet Forming.

The state of residual stresses in the Cu/Steel bonded laminates after ISF deformation: An experimental analysis

The braided corrugated hose is widely used in aerospace, marine, chemical and other fields due to its good displacement compensation and vibration damping. This paper uses finite element method to explore the effect of braiding angle on the axial mechanical properties of the braided corrugated hose. The numerical results show that the axial stiffness of the braided corrugated hose is nonlinear, which can be explained in three stages. The first stage is a linear stage, and the stiffness of the bellows plays a major role. The second stage is the non-linear stage called the ‘soft characteristic’ stage and the third stage is the linear stage. The braiding angle mainly affects the ‘the soft characteristic’ stage. As the braiding angle increases, the faster the ‘soft characteristic’ changes, the greater the axial stiffness of the braided corrugated hose increases. The conclusion can provide a theoretical basis for the design of braided corrugated hoses.

Numerical study of the axial mechanical properties of braided corrugated hose with different braiding angles

To reveal the temperature rise evolution mechanism of isotropic media subjected to reciprocating motion constant-strength point heat source, various forms of analytical solutions are derived on the basis of differentiated relative scales, and non-dimensionalized parameters are designed to characterize the thermal distribution regularities by utilizing numerical calculations. Temperature rise curves of media subjected to a reciprocating motion point heat source allow similar quasi-steady-state characteristics to appear, which finally achieve a stable state, so that the values of surplus temperature oscillate around the constant time-average quantity. The time to reach quasi-steady state, the time-averaged quantity and the fluctuation amplitude of surplus temperature are comprehensively impacted by the dimensionless distance parameter γ, the convective heat transfer parameter ω and the velocity and travel parameter β. This work discusses influence rules of temperature evolution in various relative-scale media and further enriches the moving heat source theory.

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Dacheng Huang

Papers

The state of residual stresses in the Cu/Steel bonded laminates after ISF deformation: An experimental analysis

Numerical study of the axial mechanical properties of braided corrugated hose with different braiding angles

Analytical Solutions to Temperature Field in Various Relative-Scale Media Subjected to a Reciprocating Motion Point Heat Source