Shock Amplifier Research Articles

Behavior of Polymeric Substrates and Sintered Silver Printed Hybrid Electronic Assemblies Subject to Extreme Acceleration Levels and Elevated Temperatures

Abstract This paper focuses on the response of printed hybrid electronic (PHE) assemblies with polymeric substrates and additively manufactured sintered silver electrical traces subject to extreme mechanical shocks (up to 100,000 g) and high temperatures (up to 150 °C). The substrates are hemispherical domes of injection-molded polycarbonate and polysulfone thermoplastics. Trace deposition onto the domes is accomplished by a novel process that combines conventional milling with extrusion printing to recess silver traces and dielectric insulation within the surface of the substrate. Mechanical shock testing is performed using an accelerated-fall drop tower equipped with a dual mass shock amplifier (DMSA) able to generate accelerations from 10,000 g up to 100,000 g with pulse durations of ∼0.05–0.1 ms and impact velocities of 6.5–20.5 m/s. Specimen performance is characterized by electrical and physical testing before and after testing. While polycarbonate domes survive multiple drops at all acceleration levels and temperatures, they are sensitive to heat and susceptible to warping and structural deformation at 150 °C which can compromise trace performance. Polysulfone domes can survive these temperatures without issue, but are less shock resistant and only survive 3–4 drops at 100,000 g (compared to 30+ for polycarbonate domes). Trace resistance is used as a metric to assess trace performance. All traces exhibit progressive long-term degradation over the course of multiple shocks, followed by instantaneous discontinuity during the final shock event. Trace failure (defined as the doubling of static trace resistance) occurs at ∼105–106 J/kg cumulative impact energy for all acceleration levels.

Merchants of Debt at the Extreme Overnight: Re-Considering Monetary Theories via Rollover-Induced Interbank Frictions

ABSTRACT Banks’ refusal to roll over short-term interbank debts has received increased attention since the global financial crisis. Yet, heterodox monetary theories ignore interbank transactions and rollover channels despite recognising the importance of banks’ debt-renewal practices. Against this backdrop, this research contextualises banks’ refinancing vulnerabilities within heterodox monetary theories and relates them to the literature on rollover-induced interbank frictions. This study also reveals a further shock amplifier. Due to the interplay between maturity-rollover and market-funding liquidity cycles, a rollover-circuit may emerge. This circuit may lead to additional threats to the operation of the interbank market and financial stability, compelling monetary theories not to further neglect banks’ refinancing issues.

The Impacts of Credit Standards on Aggregate Fluctuations in a Small Open Economy: The Role of Monetary Policy

Empirical evidence demonstrates that credit standards, including lending margins and collateral requirements, move in a countercyclical direction. In this study, we construct a small open economy model with financial frictions to generate the countercyclical movement in credit standards. Our analysis demonstrates that countercyclical fluctuations in credit standards work as an amplifier of shocks to the economy. In particular, the existence of endogenous credit standards increases output volatility by 21%. We also suggest three alternative tools for policymakers to dampen the effects of endogenous credit standards on macroeconomic volatility. First, the introduction of credit growth to the monetary policy succeeds in counteracting the fluctuation of lending, and thus decreasing the additional volatility considerably. Second, the exchange rate augmented monetary policy, if well-constructed, is considered an efficient tool to eliminate most of the additional fluctuations caused by deep habits in the banking sector. Finally, the introduction of the foreign interest augmented policy also proves successful in dampening the effect of endogenous movements in lending standards.

Bank Balance Sheets and External Shocks in Asia

In emerging Asia, banks constitute the dominant source of financing consumption and investment, and bank balance sheets comprise large gross FX assets and liabilities. This paper extends the DSGE model of Gertler and Karadi (2011) to incorporate these key features and estimates a panel vector autoregression on ten Asian economies to understand the role of the banking sector in transmitting spillovers from the global financial cycle to small open economies. It also evaluates the effectiveness of foreign exchange intervention (FXI) and other macroeconomic policies in responding to external financing shocks. External financial shocks affect net external liabilities of banks and the exchange rate, leading to changes in credit supply by banks and investment. For example, a capital outflow shock leads to a deprecation that reduces the net worth and intermediation capacity of banks exposed to foreign currency liabilities. In such cases, the exchange rate acts as shock amplifier and sterilized FXI, often deployed by Asian economies, can help cushion the economy. By contrast, with real shocks, the exchange rate serves as a shock absorber, and any FXI that weakens that function can be costly. We also explore the effectiveness of the monetary policy interest rate, macroprudential policies (MPMs) and capital flow management measures (CFMs).

Bank Balance Sheets and External Shocks in Asia: The Role of Fxi, Mpms and Cfms

In emerging Asia, banks constitute the dominant source of financing consumption and investment, and bank balance sheets comprise large gross FX assets and liabilities. This paper extends the DSGE model of Gertler and Karadi (2011) to incorporate these key features and estimates a panel vector autoregression on ten Asian economies to understand the role of the banking sector in transmitting spillovers from the global financial cycle to small open economies. It also evaluates the effectiveness of foreign exchange intervention (FXI) and other macroeconomic policies in responding to external financing shocks. External financial shocks affect net external liabilities of banks and the exchange rate, leading to changes in credit supply by banks and investment. For example, a capital outflow shock leads to a deprecation that reduces the net worth and intermediation capacity of banks exposed to foreign currency liabilities. In such cases, the exchange rate acts as shock amplifier and sterilized FXI, often deployed by Asian economies, can help cushion the economy. By contrast, with real shocks, the exchange rate serves as a shock absorber, and any FXI that weakens that function can be costly. We also explore the effectiveness of the monetary policy interest rate, macroprudential policies (MPMs) and capital flow management measures (CFMs).

Financial Deepening, Terms of Trade Shocks, and Growth Volatility in Low-Income Countries

This paper contributes to the literature by looking at the possible relevance of the structure of the financial system—whether financial intermediation is performed through banks or through markets—for macroeconomic volatility, against the backdrop of increased policy attention on strengthening resilience. Since low-income countries (LICs) are the most vulnerable to large and frequent terms of trade shocks, this paper focuses on a sample of 38 LICs over the period 1978–2012. It finds that banking sector development acts as a shock absorber in poor countries, dampening the transmission of terms of trade shocks to growth volatility. Expanding the sample to 121 developing countries confirms this result, although the role of shock absorber reduces as economies grow richer. By contrast, for most economies, stock market development appears neither to be a shock absorber nor a shock amplifier. These findings are consistent across a range of econometric estimators, including fixed effects, system GMM, and local projection estimates.JEL Codes: F40, G20, O10.

Formation of Multi-Stage Economies and Trade Credit: Who Amplifies Contagion Risk?

I develop a simple contract-theoretic model of multi-stage economies to address the nexus between trade credit, bank credit and balance-sheet contagion. First, I show that competitive markets in which heterogeneous price-taker firms compete strategically by setting trade credit settlements have a unique symmetric equilibrium which dictates the production flow along the chains. Second, I reconcile the conflicting evidence on the role of credit chains either as shock absorber or shock amplifier with a testable condition. I use the condition to argue that typical rationing used by banks (i.e. richer firms obtaining more credit) may worsen the chains' resilience to exogenous shocks (such as the first-order effects of COVID-19) unless sufficiently aggressive to rarefy the trade-credit network.

The role of financial shocks in business cycles with a liability side financial friction

The paper investigates the role of investment specific technology shock within the particular type of financial friction of Gertler and Karadi (2011) and the impact of direct financial shock into this, such as a net worth shock, using US data. The paper explicitly shows how the bank balance sheet effect of counter cyclical movement of capital price attenuates such investment shocks and the extent depends on the type of financial shocks included in the model. Because of the construction of capital quality shock in such financial friction model, we need to incorporate a direct net worth shock while analysing the role of financial shock. This highlights finance sector as a fundamental source of shocks apart from amplifier of shocks originating in elsewhere of the economy.

Formation of Multi-Sector Economies and Trade-Credit: Can Banks Amplify Contagion Risk?

In this paper we develop a simple model of endogenous formation of input-output economies to address the theoretical nexus between trade-credit, bank credit and credit contagion. We make two contributions. First, we show that competitive markets in which heterogeneous price-taker firms compete strategically by setting trade-credit maturities have a unique symmetric equilibrium in trade-terms and the equilibrium dictates the production flow along the supply chains. Secondly, we find that the network can have a role either as shock absorber or shock amplifier and this is determined by a testable condition which holds for a general class of trade-credit networks. On these grounds, we argue that the proportional credit rationing used by banks (i.e., richer borrowers obtain larger loans) may have ambiguous effects on systemic vulnerability. In fact, if for intermediate levels of bank-credit only a subset of firms substitute trade-credit in favor of bank-credit, the bank may worsen the quality of the inter-firm credit network, thus increasing the systemic vulnerability above the contagion threshold.

Simulation of Secondary Contact to Generate Very High Accelerations

This paper investigates the design of a typical commercially available drop system for generating very high shock and drop accelerations. Some commercially available drop towers produce accelerations greater than 5000 G by utilizing the dynamics of secondary impact, using an attachment termed a dual mass shock amplifier (DMSA). Depending on the design, some DMSAs are capable of repeatedly generating accelerations as high as 100,000 G. The results show that a finite element model (FEM) can capture the peak acceleration for the drop tower and the DMSA within 15%. In this paper, a detailed description of the test equipment and modeling techniques is provided. The effects of different design parameters, such as table mass, spring stiffness, and programmer material properties, on the drop profile, are investigated through parametric modeling. The effects of contact parameters on model accuracy are explored, including constraint enforcement algorithms, contact stiffness, and contact damping. Simple closed-form analytic models are developed, based on the basic principles of a single impact and the dynamics of secondary impact. Model predictions are compared with test results. Details of the test methodology and simulations guidelines are provided. Detailed finite element analysis (FEA) is conducted and validated against the experimental tests and compared to the simplified theoretical simulations. Benefits in exploring FEM to simulate contact between materials can be extrapolated to different architectures and materials such that with minimal experimental validation impact acceleration can be determined.

Commodity Price Cycles: The Perils of Mismanaging the Boom

Commodity-exporting countries have significantly benefited from the commodity price boom of recent years. At the current juncture, however, uncertain global economic prospects have raised questions about their vulnerability to a sharp fall in commodity prices and the policies that can shield it from such a shock. To address these questions, this paper takes a long term (4 decade) view at emerging markets' commodity dependence, the history of commodity price busts and the role of policies in mitigating or amplifying their economic impact. The paper highlights the stark difference in trends between Latin America - one of the most vulnerable regions given its high, and rising, commodity dependence - and emerging Asia - which has evolved from being a net exporter to a net importer of commodities in the last 40 years. We find evidence, however, that while commodity dependence is an important ingredient, a country's ultimate degree of vulnerability to commodity price shocks is to a great extent determined by the flexibility and quality of its policy framework. Policies in the run-up of sharp terms-of-trade drops - especially when those are preceded by booms - play a particularly important role. Limited exchange rate flexibility, a weak external position, and loose fiscal policy tend to amplify the negative effects of these shocks on domestic output. Financial dollarization also appears to act as a shock amplifier.

The Dynamics of Multiple Pair-Wise Collisions in a Chain for Designing Optimal Shock Amplifiers

The major focus of this work is to examine the dynamics of velocity amplification through pair-wise collisions between multiple masses in a chain, in order to develop useful machines. For instance low-cost machines based on this principle could be used for detailed, very-high acceleration shock-testing of MEMS devices. A theoretical basis for determining the number and mass of intermediate stages in such a velocity amplifier, based on simple rigid body mechanics, is proposed. The influence of mass ratios and the coefficient of restitution on the optimisation of the system is identified and investigated. In particular, two cases are examined: in the first, the velocity of the final mass in the chain (that would have the object under test mounted on it) is maximised by defining the ratio of adjacent masses according to a power law relationship; in the second, the energy transfer efficiency of the system is maximised by choosing the mass ratios such that all masses except the final mass come to rest following impact. Comparisons are drawn between both cases and the results are used in proposing design guidelines for optimal shock amplifiers. It is shown that for most practical systems, a shock amplifier with mass ratios based on a power law relationship is optimal and can easily yield velocity amplifications of a factor 5–8 times. A prototype shock testing machine that was made using above principles is briefly introduced.

The Dynamics of Multiple Pair-Wise Collisions in a Chain for Designing Optimal Shock Amplifiers

The major focus of this work is to examine the dynamics of velocity amplification through pair-wise collisions between multiple masses in a chain, in order to develop useful machines. For instance low-cost machines based on this principle could be used for detailed, very-high acceleration shock-testing of MEMS devices. A theoretical basis for determining the number and mass of intermediate stages in such a velocity amplifier, based on simple rigid body mechanics, is proposed. The influence of mass ratios and the coefficient of restitution on the optimisation of the system is identified and investigated. In particular, two cases are examined: in the first, the velocity of the final mass in the chain (that would have the object under test mounted on it) is maximised by defining the ratio of adjacent masses according to a power law relationship; in the second, the energy transfer efficiency of the system is maximised by choosing the mass ratios such that all masses except the final mass come to rest following impact. Comparisons are drawn between both cases and the results are used in proposing design guidelines for optimal shock amplifiers. It is shown that for most practical systems, a shock amplifier with mass ratios based on a power law relationship is optimal and can easily yield velocity amplifications of a factor 5-8 times. A prototype shock testing machine that was made using above principles is briefly introduced.

A modified dual-mass amplifier for high-strain-rate testing of SIFCON in uniaxial compression

An experimental procedure is described for obtaining compressive strength data at high rates of strain for slurry-infiltrated fiber concrete (SIFCON). A Monterey Research Laboratory dual-mass shock amplifier was modified to apply short-duration compressive loads to cylindrical test samples at rates of strain from 14 to 35/s. The data obtained are compared to data from static compressive strength tests and reveal increased peak compressive stresses at lower peak strains as compared to static strength values.