Hammer Drill Research Articles

Failure analysis of two cylindrical impact pistons subjected to high velocity impacts in drilling applications

Top hammer drilling is a common method to drill holes in rock formations in mining and civil engineering applications. Failure of drilling machine components has a significant impact on the cost and period of the operation. Internal components of percussive hammers experience extreme loading conditions during their service life. The focus of the present case study is to characterize failure mechanisms of two cylindrical impact pistons subjected to impact loading. The investigated components were manufactured from two different steel grades, a surface hardened low alloyed high strength steel and a through hardened cold work tool steel.Failure of both pistons started with degradation of the impact surfaces in term of cavitation erosion and localized surface fatigue phenomena. Subsequently, chipping and removal of material from impact surfaces resulted in formation of semi-spherical holes and craters on both surfaces.Radial and hoop cracks started to develop from cavities on the impact surface. The radial cracks then propagated parallel to the impacting surface in the longitudinal direction of the piston. Once the cracks formed at the impact surface, the damage was controlled by impact fatigue. Fatigue beach marks were identified on the fracture surface of failed component.

Effects of steel fibres on hammer drilling in concrete for the installation of post-installed anchors

Dispersed short steel fibres can be used as an addition to the concrete matrix as reinforcement to improve the material's macroscopic characteristics such as tensile strength, ductility and toughness. On the other hand, fibres may lead to negative effects in terms of constructability. For post-installed anchors, the tensile performance of the concrete plays a decisive role in certain failure mechanisms, and some fundamental investigations have already been performed in this respect. Studies on the influence of steel fibres on drilling and the respective installation have not been presented yet, although the installation quality is very significant for the fastener's load-bearing performance. This study aims to provide insight into the bearing interface characteristics of post-installed anchors and the boreholes in steel fibre-reinforced concrete generated by hammer drilling. This interface is of high importance for the performance of anchorages in special concrete composites such as steel fibre-reinforced concrete. To investigate this aspect, the research investigation is based on a combination of sophisticated but practical experimental methods ranging from drilling tool performance monitoring, qualitative and quantitative wear analysis of the borehole, optical and scanning electron microscopy of the inner borehole surface. The studies yield original findings on the interaction between drilling equipment and steel fibre-reinforced concrete in the context of the installation of post-installed anchors.

Insight into dust control performance of a reverse circulation drill bit using multiphase flow simulation

ABSTRACT A feature of reverse circulation pneumatic down-the-hole (DTH) hammer drilling system is its ability to reduce the emission of respirable dust which is known to be harmful to drilling workers and equipment. The enhanced dust control performance of the drilling system requires better understanding and insight into the airflow behavior at the bottom of the borehole. To investigate the transportation and distribution of cuttings under various drilling parameters, and to evaluate the dust control performance, we conducted a series of simulations using computational fluid dynamics (CFD) multiphase modeling. Finite volume analysis was performed on a reverse circulation drill bit with an optimized structure reported in a previous study. The results show that increasing the input airflow rate can directly improve the dust control efficiency. The rising value in terms of cuttings feed concentration, rate of penetration (ROP), particle diameter, and specularity coefficient would decrease the dust control performance. Furthermore, the characteristics of the cutting distribution vary with the operating parameters and demonstrate the multiphase flow pattern in the RC-bit. This work may provide instructive insights into cutting transportation under various drilling parameters commonly considered in the drilling process and promote the development of dust suppression with efficient drilling operations.

Subsurface seismic imaging with a hammer drilling source at an exploration drilling test center in Örebro, Sweden

Abstract. Seismic imaging while drilling (SWD) technology offers possibilities of imaging ahead of the drill-bit, which could be useful for determining when to go from hammer drilling to core drilling. Also, seismic images of the surrounding rock can improve geological models which could be then used to guide drilling programs. An SWD field test was carried out in August 2020 at an exploration drilling test site in Örebro, Sweden, with the aim to determine if the signals from hammer drilling can be used for seismic imaging around the drill-bit in a hard-rock environment where the strong drill-rig noise interference is one of the main challenges. The test site had previously been investigated with various geophysical methods, geological mapping and diamond core drilling, and it therefore represented an ideal location to perform this feasibility study. After data pre-processing and cross-correlation with the trace from the geophone closest to the rig, the shot-gathers were vertically stacked over the length of a drill pipe to achieve further signal improvement. A comparison with the active seismic data shows reasonable agreement, in spite of the fact that the noise level is significant even after careful processing. However, the lack of clear reflections in the active seismic data, indicating no detectable changes in the bedrock lithology in the near surface, hinders the full assessment of the seismic signal generated with hammer drilling at this site.

Experimental and Numerical Analysis of Flow Behavior for Reverse Circulation Drill Bit with Inserted Swirl Vanes

A swirling drill bit designed with an integrated vane swirler was developed to improve reverse circulation in down-the-hole hammer drilling. Its entrainment effect and influential factors were investigated by CFD simulation and experimental tests. The numerical results exhibit reasonable agreement with the experimental data, with a maximum error of 13.68%. In addition, the structural parameters of the swirler were shown to have an important effect on the reverse circulation performance of the drill bit, including the helical angle and number of spiral blades, swirler outlet area, and the flushing nozzles. The optimal parameters for the swirling drill bit without flushing nozzles include a helical angle of 60°, four spiral blades, and the area ratio of 2, while it is about 30°, 3, and 3 for the drill bit with flushing nozzles. Moreover, the entrainment ratio of the drill bit without flushing nozzles can be improved by nearly two times compared with one with flushing nozzles under the same conditions.

Design and Performance Evaluation of an Ultralow-Power Smart IoT Device With Embedded TinyML for Asset Activity Monitoring

This article proposes a proof-of-concept device to continuously assess the usage of handheld power tools and detect construction working tasks (e.g., different drilling works) along with potential misusages, e.g., drops, with an energy-efficient architecture design. The designed device is based on Bluetooth low energy (BLE) and NFC connectivity. BLE is used to exchange data with a gateway, whereas NFC has been chosen as an energy-efficient wake-up mechanism. A temperature and humidity sensor is embedded to monitor storage conditions and an accelerometer for tool usage monitoring. The ARM Cortex-M4 core embedded in the BLE module is exploited to process the information at the edge. A Tiny Machine Learning (TinyML) algorithm is proposed to process the data directly on board and achieve low latency and high energy efficiency. The TinyML algorithm has been developed embedded in the proposed device to detect four different usage classes (tool transportation, no-load, metal, and wood drilling). A dataset containing more than 280 min of three-axis accelerations during different activities has been acquired with the device attached to a construction rotary hammer drill and used to train and validate the algorithm. A neural architecture search has been performed to optimize the trade-off between accuracy and complexity, achieving an accuracy of 90.6% with a model size of roughly 30 kB. The experimental results showed an ultralow power consumption in sleep mode of 550 nA and a peak power consumption of 8 mA while running TinyML on the edge. This results in a balanced combination of edge processing capabilities and low power consumption, enabling to obtain a smart Internet of Things (IoT) device in the field with a long lifetime of up to four years in operation and 17 years in shelf mode with a standard 250-mAh coin battery. This work enables a long battery lifetime operation of device degradation and utility analysis, further closing the gap between edge processing and fine granularity data evaluation.

Considering Manufacturing in Functional Modelling - Case Study on Combination of Simulation-Driven Design with Design-for-Manufacture

In engineering design, function fulfilment is the raison d'être of a product. However, economic boundary conditions have to be taken into consideration as well to enable marketability of the product. In this paper, a case study is presented, where function-based engineering using the Simulation-Driven Design is linked with Design-for-Manufacture as an example for economic design through qualitative modelling. The qualitative modelling with the Contact and Channel Approach aims to support the integrated consideration of functional requirements and manufacturing boundary conditions. The linked approaches are applied in the development of a test rig for hammer drills. It shows how Design-for-Manufacture can be considered early in conceptual decisions in embodiment design by separating functional embodiment and residual structure through qualitative modelling. The freeze-unfreeze strategy is presented as a possibility to identify potential for Design-for-Manufacture to meet economic boundary conditions in conceptual design without reducing the functionality of the system. Further research possibilities regarding qualitative modelling to support functional and economic design are uncovered.

Experimental and Numerical Study on Air Flow Behavior for a Novel Retractable Reverse Circulation Drill Bit of Casing-while-Drilling (CwD)

A reverse circulation Down-The-Hole (DTH) hammer drill bit in Casing-while-Drilling (CwD) processes is designed and applied to drilling under complicated formation. The drill bit is a special retractable drill bit with an exclusive reverse circulation gas channel. Using numerical simulations and experiments, the influence of the gas channel structure parameters of the drill bit, including the inner jet nozzles, flushing nozzles, suction channel, and other parameters, on its reverse circulation performance is analyzed, and the optimal gas channel structure parameters of the drill bit are determined to improve the reverse circulation effect. The results show that the flushing nozzles and inner jet nozzles have an important influence on entrainment performance. The entrainment rate η decreases as the flushing nozzle diameter increases and decreases as the inner jet nozzle diameter increases. An increase in the suction channel diameter can improve the reverse circulation effect of the drill bit. The spiral slot drill bit is more conducive to air being sucked into the central channel in the form of spiral flow, so it can improve the entrainment performance. The entrainment rate η can reach 23.4% with the optimum structured drill bit.

Design, Fabrication, and Performance Analysis of Intelligent Mesoscale Capacitive Accelerometer for Vibration Measurement

Abstract This paper portrays an accelerometer as a motion sensor used to measure acceleration, vibration, and tilt angles which plays a vital role in the constructional field, inertial measurements, automotive safety system, biomedical, and yet other safety applications. A small packaged accelerometer can be made larger in size by acquiring an external power source or battery. The designed micro-accelerometer is fabricated using clean room technology, which is not quite cost effective, and even the silicon base is replaced by steel because of steel’s high yield strength and low cost to fabricate a mesoscale accelerometer. Design parameters are optimized by a Decision Tree Algorithm where the optimized dimensions are used to model the mesoscale accelerometer in INTELLISUITE 8.6 software. A Wire-cut discharger is used for the fabrication of mechanical elements of an accelerometer with a spring steel foil to reduce fabrication cost. Finally, the fabricated accelerometer with a mesoscale was made to undergo experimentation with a hammer drill and compared with simulation results to evaluate its performance in a harsh construction environment. 0.576 (μm/g) of mechanical sensitivity and 0.629 (pF/g) of electrical sensitivity is achieved.

Triggering of earthquakes at Koyna, India and hammer drilling for the pilot borehole

Triggering of earthquakes at Koyna, India and hammer drilling for the pilot borehole

Underwater Power Tools for In Situ Preservation, Cleaning and Consolidation of Submerged Archaeological Remains

In situ protection and conservation of the Underwater Cultural Heritage are now considered a primary choice by the scientific community to be preferred, when possible, over the practice of recovery. The conservation of the artefacts within their environmental context is essential in fact for a correct interpretation of archaeological presences and to preserve their true value intact for future generations. However, this is not an easy task because modern technological equipment is necessary to make the work carried out by underwater restorers and archaeologists faster and more efficient. To this end, the paper presents three innovative underwater power tools for the cleaning, conservation, and consolidation activities to be performed in submerged archaeological sites. The first one is an underwater cleaning brush tool for a soft cleaning of the underwater archaeological structures and artefacts; the second one is a multifunctional underwater hammer drill suitable to be used as a corer sampler, chisel, or drill; the last one is an injection tool specifically designed to dispense mortar underwater for consolidation techniques of submerged structures.

Thermoelectric energy harvesting electronic skin (e-skin) Patch with reconfigurable carbon nanotube clays

Advances in the electronic skin (e-skin) have led to the next electronic paradigm, which involves the integration of devices with the human body. However, skin-adaptable permanent power technology is immature in terms of improving sensitivity to explosion hazard and facilitating wire/wireless charging, thus restricting the practical application of the e-skin. Here, we present a thermoelectric clay made of carbon nanotubes (CNTs) and non-ionic surfactants as viscous additives for use in skin-adaptable permanent power sources for the e-skin. The controlled kneading ratio of the CNT to the viscous additive (1:5) makes the thermoelectric clay reconfigurable with a lower elastic modulus than that of the human skin, providing skin adaptability with high elongation up to 100% and remendability after chapping. Through chemical doping, we produced n-type and p-type thermoelectric clays, optimized their electrical conductivities and Seebeck coefficients, and obtained enhanced ZT values. The thermoelectric output power was preserved over 80% of the initial value even more than one year. Finally, a skin-adaptable thermoelectric power patch for the e-skin was fabricated with five pairs of n-type and p-type thermoelectric clays, and its performance was demonstrated. The patch was successfully operated under severe folding, twisting, stretching on the human skin and even when punctured state at room temperature. Thermoelectric energy harvesting electronics skin (e-skin) patch consisted reconfigurable p-n thermoelectric clay matrix which is highly skin-adaptable and mechanically durable for extreme situation such as hammer impact and drilling. • Thermoelectric energy harvesting electronic skin (e-Skin) patch with reconfigurable carbon nanotube clay is presented for skin-adaptable semi-permanent power supply with mechanical durability for the e-skin. • The reconfigurable thermoelectric clay made of chemically doped CNTs and viscous additive is highly soft, stretchable and repairable and even air-stable. • The thermoelectric e-Skin patch with the reconfigurable CNT clays has skin-adaptability with mechanical durability against hammer hitting and even puncturing.

The influence of human interaction on the vibration of hand-held human-machine systems – The effect of body posture, feed force, and gripping forces on the vibration of hammer drills

In hand-held human machine systems the biodynamic response of the human hand arm system influences the overall dynamic behavior. The biodynamic response of the hand arm system is affected by several influencing factors. These influencing factors include the feed force, body posture, gripping force, and anthropometric properties. In present studies the importance of the gripping force on the biodynamic response is highlighted. In the state of the art; however, the magnitude of gripping forces as well as the influence of the human factors body posture and feed force on hammer drills for a larger group of professional users is unclear. To analyze the influence that these human factors have on hammer drill vibrations, a study with 15 professional power tool test personnel has been conducted. Characteristic gripping force values have been measured (Median: 84 N–156 N at the main handle, 10 N–30 N on the auxiliary handle) for different feed forces (100 N, 150 N, 200 N) and body postures. Then the influence of body posture, feed force, and gripping force on the hammer drill vibration is determined. A significant influence of the body posture (ANOVA: p = .003, r = .367) on the RMS acceleration of the main handle was observed. Furthermore, the feed force has a significant influence on the vibration of the hammer-drill for some groups. The data also demonstrates that for increasing gripping forces, the RMS of the acceleration and frequency weighted acceleration ahv on the main and auxiliary handle decrease. The findings of this study represent a starting point for the development of adjustable hand-arm models for the reproducible vibration assessment of power tools.

Influence of different drilling methods on the behavior of post‐installed mechanical fasteners in uncracked and cracked concrete

AbstractInnovative drilling methods gain importance in the field of post‐installed fasteners. For this reason, users, customers and manufacturers demand methods other than the standard drilling procedure of hammer drilling, as they are hollow drilling with included cleaning and diamond drilling without emitting drill dust. One open question regarding these drilling methods is the equivalence of the behavior under the conditions of cracked concrete over the entire lifetime. These conditions are typically tested in the crack movement test, which simulates the real behavior of a fastener in cracked concrete over a designed lifetime of 50 years. In this contribution, the example of a post‐installed mechanical bolt anchor is used to explain how a difference in the behavior is a consequence of different drilling methods in noncracked concrete, in cracked concrete and in cracked concrete in which the crack is cycled. Additionally, it is observed that the behavior in the crack cycling test is significantly influenced by the drilling method.

Analysis of factors influencing the productivity of hammer drilling – user forces, human fatigue, drilling direction, and drill bit

In order to be able to develop a hammer drill with which the user can work as ergonomically and productively as possible, the relevant influencing factors must be known. In addition to the unknown influence of the drilling direction, there is a lack of understanding of the relations between user forces, human fatigue, and productivity. To analyze these relations, an experiment was carried out with 15 professional users. First, the influence of feed force, drilling direction, and drill bit on the rate of penetration was examined. Taking into account the rate of penetration and human fatigue, it was then investigated which of the three feed forces produces the highest productivity. Furthermore, the lateral forces applied by the participants during the drilling process were analyzed. Based on the study, it was found that the drilling direction (p < .001, r = −0.198) and the drill bit type (p < .041, r = −0.16) have a significant influence on the rate of penetration. Moreover, it was found that the rate of penetration tends to increase with higher feed forces, however, the theoretical cumulative drilling meters decrease when taking user fatigue into account. Finally, the experiment showed that the participating professionals applied lateral forces (Mdn = 16.7 N) of 13% to the feed force when working with a hammer drill. On the basis of this knowledge, investigations can be done to analyze the influences of lateral forces on the drilling process. The findings help drill and hammer drill manufacturers in testing and development processes. For craftsmen, on the other hand, the knowledge helps to perform the task as ergonomically and time-efficiently as possible.

Improvement of the Hammer Drill Performance (Algerian Quarries Conditions)

Abstract The factors which influence the performance characteristics of a hammer drill are examined; drilling data are analyzed to determine these factors. Methods for selecting the appropriate drilling are also highlighted. Two models are used in order to compare optimal drilling parameters. The main one is the machine output.

Statistical Evaluation of the Perpendicularity of Boreholes in Concrete for Post-Installed Fasteners

The form and the perpendicularity of boreholes influence the ultimate behaviour of post-installed fasteners and are restricted with regard to the concrete surface to 5° in Europe and to 6° in the United States in various regulations (e.g., EAD 330232-00-0601 resp. ACI 355.2-19). It is assumed that the deviation of the borehole from the vertical axis has an effect on the load transfer behaviour of an anchorage. This article investigates on the perpendicularity of vertically downward drilled boreholes using different drilling tools considering hammer drilling, hollow drilling and diamond core drilling. It can be shown that the requirements of e.g., EAD 330232-00-0601 of a maximum deviation to the concrete surface of 5° can be fulfilled for approximately 95% of the determined values for different drilling methods. This is based on a considerable number of measurements (generated from drilled boreholes) in different concrete types. As a result, a detailed statistical evaluation is provided to describe the borehole perpendicularity by means of statistical methods.

R2: Drilling into concrete: Effect of feed force on handle vibration and productivity

Approximately 1.6 million commercial construction workers in the US use rotary hammer drills for drilling into concrete to insert anchor bolts or rebar. The exposure to vibration may lead to hand-arm vibration syndrome and other musculoskeletal disorders depending on handle vibration acceleration level, hand grip force, and duration of exposure. There is little information on the relationship between feed force (FF), e.g., the push force applied by the worker, and handle vibration. A robotic test bench for rotary hammer drills was used to evaluate the effects of different FF on handle vibration and productivity (e.g., penetration rate and holes drilled). Increasing FF from 95 to 163 N was associated with an increase in total weighted handle vibration (ahv) of 7.2–8.5 m/s2 (slope, p < 0.001) but from 163 to 211 N there was no change in vibration level (slope, p = 0.17). Increasing FF from 95 to 185 N was associated with an increase in penetration rate of 7.2–8.5 m/s2 (slope, p < 0.001) but from 185 to 211 N there was no change in penetration rate (slope, p = 0.49). Based on the maximum allowable duration of exposure to hand vibration, specified by the ISO and ACGIH Action Limits, and the penetration rate, the drilling productivity, in m drilled per day, is greatest for the lowest FF tested. Contractors and construction workers should be informed that when drilling into concrete, the lowest exposure to harmful hand vibration and the best overall productivity occurs when the lowest operational FF is applied during hammer drilling.

Design process of executive elements in stroke mechanisms based on rammer’s deformations and stress modeling

The article deals with the strength calculation issues of products by example of rammer under short-term loads in hammer drill. Based on finite element analysis’ results of the rammer geometrical model, it is proposed to select a material with a strength limit significantly exceeding the allowable residual stresses inside the rammer. The harmonic analysis allows us to estimate the rammer’s strength. The dynamic coefficient may be calculated by the use of Vibran 2.0 device (amplitude and signal frequency) and by calculation results of the maximum displacement. The FreeCAD software package was used for this. It allows to create internal scripts to automatically search for the optimal design parameters. A method of determining mechanism’s static load and its dynamic coefficient under periodic impact loads has been developed. Static loads calculations and harmonic analysis according to the developed method allow to determine structural strength of the product, to select the rammer’s material and to find the dynamic coefficient (which takes into account the stroke loads in calculations). The pro-posed calculation method may be used not only to solve the describing problem, but also for a whole class of problems related to stroke loading, where such parameters as application time of force or duration time of force’s impulse are important.

Background for engineering a continuous-operation soil drifter

The paper discusses the feasibility of combining compaction and excavation processes in hole making. The continuous loop of hole-making and soil removal from hole pipe by compressed air return flow is proposed. Usability of an air hammer drill with elastic valve in the air distribution system in capacity of a drifter motor is examined. Using a physical dimension model with piston 4 kg in weight, the author refines energy and frequency performance of the pulse generator given the backpressure in the exhaust chamber. The experimental curves of the percussion capacity parameters are obtained.