High-frequency shock-type vibrations (HFVs) from, e.g., impact wrenches with a frequency content mainly above 1250 Hz have long been suspected to cause a significant number of vibration injuries, HAVS. These vibrations are unregulated in the current standard for risk estimation, ISO 5349-1; thereby, the risk of injury is suspected to be underestimated. The objective of this study was to investigate the effects on finger tissue subjected to HFVs similar to those from impact wrenches by using a 2D finite element model of a fingertip. The model was validated through experiments. Using the input acceleration from the experiments, the model predicted high pressure variation and particular negative pressures at levels close to 0.1 MPa (1 Bar) or more, which are levels where cavitation in liquid can occur, with a detrimental effect on biological systems.
Cost and time for stamping die tryouts are significant within the car industry. A major contributing factor is that elastic deflections of stamping dies and presses are usually not considered during the virtual die design and forming simulation phase. Active surfaces of stamping dies are only cambered based on previous experiences of tool types and stamping presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new sheet materials. This leads to component deviations and often several loops of tool adjustments are needed. Previously partners within the SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of stamping presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. In this paper numerical substitutive stamping press models are described which are capable of compensating for measured stamping press dynamics. The result show that a numerical compensated tool can improve the contact by over 80% compared to the corresponding contact without compensation.
Cost and time for die tryout are significant within the car industry, and elastic deflections of dies and presses are most commonly not considered during the virtual die design and forming simulation phase. Because of this, active surfaces of stamping dies are only cambered based on previous experiences of tool types and presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new materials. Partners within the Eureka SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. Important breakthroughs in recent years enabling the cambering methodology consists of efficient simulation strategies for full scale simulations with elastic dies and optimization techniques for creating substitutive press structures based on measurements. Furthermore, modern press deflection measurement methods are beneficial in applications such as Industry 4.0, predictive maintenance, product quality control, etc. through a more advanced understanding and live monitoring of the press system.
During machining the accumulated bulk stresses induced by previous shape forming process steps, such as forging, casting or additive manufacturing and subsequent heat treatment, will be released and cause undesirable geometry errors on the final component. By considering the residual stresses during process planning a significant improvement in dimensional accuracy can be achieved. This paper presents experiences for prediction of residual stresses for components with complex geometries using the Contour method. Three sectioning procedures have been tested and a cutting strategi using Electric Discharge Machining with slow feed rate and cutting from two sides with final cut in the middle is proposed. Two Finite Element modelling strategies for 3D-models have been tested and a meshing strategy based on extrusion of the geometry from the cut plane is recommended. Further, a procedure to automate the Finite Element meshing of complex structures using the Alpha Shape algorithm is proposed. The ambition is to integrate this algorithm in procedures for automatization of the entire analysis. © 2022 The authors
When hot forging components, wear can occur in the tool after a period of use, leading to incorrect geometry in the final component. This necessitates replacing the worn tool with a new one, which is costly. The current approach is to repair the tool using machining that removes the worn surface which is less efficient from a circularity standpoint. A more sustainable approach is to maximize the tool life by carefully adjusting the material and process parameters to slow the wearing process and repair without removing material as much as the cost is justified. Factors such as sliding distance, normal forces between the billet and forging tool, and the hardness of the tool all influence wear during forging. This study focuses on analytics of the process using measurements of the tool conditions and wear simulation based on Archard's law. The tool was analysed using stress, geometry, and hardness measurements. Several strategies to maintain or increase hardness, thereby extending tool life, are proposed. These include adjusting heat treatment before forging, modifying machining parameters, extending cooling time during hot forging, and replacing the current coolant with a more effective one.
During machining the material removal releases residual stresses introduced by previous process steps. This causes geometric machining distortions and thereby high rejection rates and costs. By simulating the process chain it is possible to predict this type of distortions. However, this requires advanced material models and accurate process- and material data for the individual processes. In order to simplify the modelling efforts a methodology that combines the contour method with machining simulation is proposed. The methodology is validated for an aerospace component using deep layer removal X-ray diffraction and CMM measurements. The methodology will improve possibilities to reduce machining distortions. © 2018 The Authors.